The present invention relates to a temperature measuring system utilizing a microthermometer or micropyrometer. The system is particularly useful for the rapid and accurate determination of temperatures of ultra miniature areas. The present system is particularly useful in providing means to obtain rapid and precise clinical temperature measurements of cellular areas of micro dimension, e.g., a single cell, or portion of a cell, or a group of specific cells, either within or without a living body.
Devices to measure temperature by measuring changes in electrical resistance are known in the prior art. Examples of such devices are: U.S. Pat. Nos. 2,210,903; 2,711,650; 2,737,810; 2,779,917 and 2,938,385. Generally such devices utilize either a resistance thermometer or a thermistor as the temperature sensory element, or probe. Typically a resistance thermometer includes a metal or semi-conductor material. Metals such a platinum, nickel or copper are commonly used. Thermistors typically utilize a solid semi-conductor ceramic-like element, e.g., oxides of manganese, cobalt, copper, uranium, iron, zinc and magnesium.
Generally electrically conducting materials become more resistant to the passage of electrical current as temperature increases. The increase in electrical resistance is, within certain determinable limits, proportional to the increase in temperature. Thus, a temperature sensing element, or probe, may be used to determine temperature by measurement of increases or decreases in the electrical resistance of the probe.
To facilitate precise temperature measurement the temperature probe is typically incorporated as part of a resistance measuring circuit. If a source of constant potential is available, the measuring circuit may merely include an ammeter, the change in electrical current reflecting the change in resistance in the circuit. A resistance bridge network, for example, a meter bridge or a Wheatstone bridge, may be used. A bridge circuit allows a comparison of resistances. In such circuits the electrical resistance of the temperature probe is accurately determined by evaluating the resistance of the probe in a balanced bridge circuit and the temperature of the probe is derived from the electrical resistance of the probe. In a particularly useful embodiment, the resistance of the temperature probe may be determined by instrument and directly read as temperature.
The present invention is particularly useful in the study of cellular or membrane phenomena wherein the accurate temperature of a cell or part of a cell is to be determined. The extremely small temperature sensory element, or probe, of the present invention allows cell penetration without causing serious injury to the cell, or disrupting the cell structure or function. The study of cellular temperature response has heretofore been confined to the study of groups of large cells because of the large size of prior art probes. In the past such limitations were particularly severe in the study of vertebrate brain, spinal cord and retina cells where the vast majority of cells are smaller than about 20 microns in diameter. The present invention is particularly useful as a tool for studying the effect of heat and temperature changes in such small cells.
It is envisioned that the present invention can be utilized to measure blood flow in capillaries or the rate of air flowing through a single alveoli in the lung. The probe portion of the present invention typically has a diameter about one-fiftieth of the diameter of a human hair.
The present invention facilitates the study of ultra small areas, cellular or subcellular. As used herein the term ultra small area means an area less than about 20 microns in diameter. It is postulated that the present invention may open research vistas not heretofore open which will encompass the study of the effects of temperature changes within a particular cell or particular cells within a group of cells.
The fabrication of microcapillary tubes aptly suited to use in the present invention is described in U.S. Application Ser. No. 693,725, filed Jan. 23, 1985, entitled, "METHOD AND APPARATUS FOR PRODUCING GLASS TUBING OF A NARROWED DIAMETER". The present invention is co-inventor of that application. The disclosure of said application is incorporated herein by reference.